scholarly journals Seasonal Forecasts of Major Hurricanes and Landfalling Tropical Cyclones using a High-Resolution GFDL Coupled Climate Model

2016 ◽  
Vol 29 (22) ◽  
pp. 7977-7989 ◽  
Author(s):  
Hiroyuki Murakami ◽  
Gabriel A. Vecchi ◽  
Gabriele Villarini ◽  
Thomas L. Delworth ◽  
Richard Gudgel ◽  
...  
Keyword(s):  
High Resolution ◽  
Wind Speed ◽  
North Atlantic ◽  
North Pacific ◽  
Climate Model ◽  
The United States ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Seasonal Forecasts ◽  
The North ◽  
The North Atlantic

Abstract Skillful seasonal forecasting of tropical cyclone (TC; wind speed ≥17.5 m s−1) activity is challenging, even more so when the focus is on major hurricanes (wind speed ≥49.4 m s−1), the most intense hurricanes (category 4 and 5; wind speed ≥58.1 m s–1), and landfalling TCs. This study shows that a 25-km-resolution global climate model [High-Resolution Forecast-Oriented Low Ocean Resolution (FLOR) model (HiFLOR)] developed at the Geophysical Fluid Dynamics Laboratory (GFDL) has improved skill in predicting the frequencies of major hurricanes and category 4 and 5 hurricanes in the North Atlantic as well as landfalling TCs over the United States and Caribbean islands a few months in advance, relative to its 50-km-resolution predecessor climate model (FLOR). HiFLOR also shows significant skill in predicting category 4 and 5 hurricanes in the western North Pacific and eastern North Pacific, while both models show comparable skills in predicting basin-total and landfalling TC frequency in the basins. The improved skillful forecasts of basin-total TCs, major hurricanes, and category 4 and 5 hurricane activity in the North Atlantic by HiFLOR are obtained mainly by improved representation of the TCs and their response to climate from the increased horizontal resolution rather than by improvements in large-scale parameters.

scholarly journals Decadal prediction of the North Atlantic subpolar gyre in the HiGEM high-resolution climate model

2017 ◽  
Vol 50 (3-4) ◽  
pp. 921-937 ◽  
Author(s):  
Jon Robson ◽  
Irene Polo ◽  
Dan L. R. Hodson ◽  
David P. Stevens ◽  
Len C. Shaffrey
Keyword(s):  
High Resolution ◽  
North Atlantic ◽  
Climate Model ◽  
Decadal Prediction ◽  
Subpolar Gyre ◽  
The North ◽  
North Atlantic Subpolar Gyre ◽  
The North Atlantic

scholarly journals The Ocean Carbon States Database: a proof-of-concept application of cluster analysis in the ocean carbon cycle

2018 ◽  
Vol 10 (1) ◽  
pp. 609-626 ◽  
Author(s):  
Rebecca Latto ◽  
Anastasia Romanou
Keyword(s):  
Data Mining ◽  
Wind Speed ◽  
Carbon Cycle ◽  
Southern Ocean ◽  
North Atlantic ◽  
Climate Model ◽  
Proof Of Concept ◽  
The North ◽  
The North Atlantic ◽  
Ocean Carbon

Abstract. In this paper, we present a database of the basic regimes of the carbon cycle in the ocean, the “ocean carbon states”, as obtained using a data mining/pattern recognition technique in observation-based as well as model data. The goal of this study is to establish a new data analysis methodology, test it and assess its utility in providing more insights into the regional and temporal variability of the marine carbon cycle. This is important as advanced data mining techniques are becoming widely used in climate and Earth sciences and in particular in studies of the global carbon cycle, where the interaction of physical and biogeochemical drivers confounds our ability to accurately describe, understand, and predict CO2 concentrations and their changes in the major planetary carbon reservoirs. In this proof-of-concept study, we focus on using well-understood data that are based on observations, as well as model results from the NASA Goddard Institute for Space Studies (GISS) climate model. Our analysis shows that ocean carbon states are associated with the subtropical–subpolar gyre during the colder months of the year and the tropics during the warmer season in the North Atlantic basin. Conversely, in the Southern Ocean, the ocean carbon states can be associated with the subtropical and Antarctic convergence zones in the warmer season and the coastal Antarctic divergence zone in the colder season. With respect to model evaluation, we find that the GISS model reproduces the cold and warm season regimes more skillfully in the North Atlantic than in the Southern Ocean and matches the observed seasonality better than the spatial distribution of the regimes. Finally, the ocean carbon states provide useful information in the model error attribution. Model air–sea CO2 flux biases in the North Atlantic stem from wind speed and salinity biases in the subpolar region and nutrient and wind speed biases in the subtropics and tropics. Nutrient biases are shown to be most important in the Southern Ocean flux bias. All data and analysis scripts are available at https://data.giss.nasa.gov/oceans/carbonstates/ (DOI: https://doi.org/10.5281/zenodo.996891).

scholarly journals Seasonal Predictions of Tropical Cyclones Using a 25-km-Resolution General Circulation Model

2013 ◽  
Vol 26 (2) ◽  
pp. 380-398 ◽  
Author(s):  
Jan-Huey Chen ◽  
Shian-Jiann Lin
Keyword(s):  
Tropical Cyclones ◽  
General Circulation Model ◽  
North Atlantic ◽  
Intensity Distribution ◽  
North Pacific ◽  
General Circulation ◽  
Circulation Model ◽  
Geophysical Fluid Dynamics Laboratory ◽  
The North ◽  
The North Atlantic

Abstract Retrospective seasonal predictions of tropical cyclones (TCs) in the three major ocean basins of the Northern Hemisphere are performed from 1990 to 2010 using the Geophysical Fluid Dynamics Laboratory High-Resolution Atmospheric Model (HiRAM) at 25-km resolution. Atmospheric states are initialized for each forecast, with the sea surface temperature anomaly (SSTA) “persisted” from that at the starting time during the 5-month forecast period (July–November). Using a five-member ensemble, it is shown that the storm counts of both tropical storm (TS) and hurricane categories are highly predictable in the North Atlantic basin during the 21-yr period. The correlations between the 21-yr observed and model predicted storm counts are 0.88 and 0.89 for hurricanes and TSs, respectively. The prediction in the eastern North Pacific is skillful, but it is not as outstanding as that in the North Atlantic. The persistent SSTA assumption appears to be less robust for the western North Pacific, contributing to less skillful predictions in that region. The relative skill in the prediction of storm counts is shown to be consistent with the quality of the predicted large-scale environment in the three major basins. It is shown that intensity distribution of TCs can be captured well by the model if the central sea level pressure is used as the threshold variable instead of the commonly used 10-m wind speed. This demonstrates the feasibility of using the 25-km-resolution HiRAM, a general circulation model designed initially for long-term climate simulations, to study the impacts of climate change on the intensity distribution of TCs.

scholarly journals A Mechanism of Internal Decadal Atlantic Ocean Variability in a High-Resolution Coupled Climate Model

2015 ◽  
Vol 28 (19) ◽  
pp. 7764-7785 ◽  
Author(s):  
Matthew B. Menary ◽  
Daniel L. R. Hodson ◽  
Jon I. Robson ◽  
Rowan T. Sutton ◽  
Richard A. Wood
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
Climate Models ◽  
Climate Model ◽  
Heat Content ◽  
Coupled Climate Model ◽  
North Atlantic Current ◽  
The North ◽  
The North Atlantic

Abstract The North Atlantic Ocean subpolar gyre (NA SPG) is an important region for initializing decadal climate forecasts. Climate model simulations and paleoclimate reconstructions have indicated that this region could also exhibit large, internally generated variability on decadal time scales. Understanding these modes of variability, their consistency across models, and the conditions in which they exist is clearly important for improving the skill of decadal predictions—particularly when these predictions are made with the same underlying climate models. This study describes and analyzes a mode of internal variability in the NA SPG in a state-of-the-art, high-resolution, coupled climate model. This mode has a period of 17 yr and explains 15%–30% of the annual variance in related ocean indices. It arises because of the advection of heat content anomalies around the NA SPG. Anomalous circulation drives the variability in the southern half of the NA SPG, while mean circulation and anomalous temperatures are important in the northern half. A negative feedback between Labrador Sea temperatures/densities and those in the North Atlantic Current (NAC) is identified, which allows for the phase reversal. The atmosphere is found to act as a positive feedback on this mode via the North Atlantic Oscillation (NAO), which itself exhibits a spectral peak at 17 yr. Decadal ocean density changes associated with this mode are driven by variations in temperature rather than salinity—a point which models often disagree on and which may affect the veracity of the underlying assumptions of anomaly-assimilating decadal prediction methodologies.

scholarly journals Continued Increases in the Intensity of Strong Tropical Cyclones

2020 ◽  
Vol 101 (8) ◽  
pp. E1301-E1303 ◽  
Author(s):  
James B. Elsner
Keyword(s):  
Wind Speed ◽  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
Base Period ◽  
The North ◽  
The North Atlantic

Abstract In a 2008 paper, using satellite-derived wind speed estimates from tropical cyclones over the 25-yr period 1981–2006, we showed the strongest tropical cyclones getting stronger. We related the increasing intensity to rising ocean temperatures consistent with theory. Oceans have continued to warm since that paper was published, so the intensity of the strongest cyclones should have continued upward as well. Here I show that this is the case, with increases in the upper-quantile intensities of global tropical cyclones amounting to between 3.5% and 4.5% in the period 2007–19 relative to the earlier base period (1981–2006). All basins individually show upward intensity trends for at least one upper quantile considered, with the North Atlantic and western North Pacific basins showing the steepest and most consistent trends across the quantiles.

scholarly journals The Present-Day Simulation and Twenty-First-Century Projection of the Climatology of Extratropical Transition in the North Atlantic

2017 ◽  
Vol 30 (8) ◽  
pp. 2739-2756 ◽  
Author(s):  
Maofeng Liu ◽  
Gabriel A. Vecchi ◽  
James A. Smith ◽  
Hiroyuki Murakami
Keyword(s):  
North Atlantic ◽  
Global Climate Model ◽  
The United States ◽  
First Century ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Extratropical Transition ◽  
The North ◽  
The North Atlantic ◽  
Twenty First Century ◽  
Eastern North Atlantic

This study explores the simulations and twenty-first-century projections of extratropical transition (ET) of tropical cyclones (TCs) in the North Atlantic, with a newly developed global climate model: the Forecast-Oriented Low Ocean Resolution (FLOR) version of the Geophysical Fluid Dynamics Laboratory (GFDL) Coupled Model version 2.5 (CM2.5). FLOR exhibits good skill in simulating present-day ET properties (e.g., cyclone phase space parameters). A version of FLOR in which sea surface temperature (SST) biases are artificially corrected through flux-adjustment (FLOR-FA) shows much improved simulation of ET activity (e.g., annual ET number). This result is largely attributable to better simulation of basinwide TC activity, which is strongly dependent on larger-scale climate simulation. FLOR-FA is also used to explore changes of ET activity in the twenty-first century under the representative concentration pathway (RCP) 4.5 scenario. A contrasting pattern is found in which regional TC density increases in the eastern North Atlantic and decreases in the western North Atlantic, probably due to changes in the TC genesis location. The increasing TC frequency in the eastern Atlantic is dominated by increased ET cases. The increased density of TCs undergoing ET in the eastern subtropics of the Atlantic shows two propagation paths: one moves northwest toward the northeast coast of the United States and the other moves northeast toward western Europe, implying increased TC-related risks in these regions. A more TC-favorable future climate, evident in the projected changes of SST and vertical wind shear, is hypothesized to favor the increased ET occurrence in the eastern North Atlantic.

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